To attain tranquil abiding we need to gain in succession nine levels of concentration on one object. These are:
1) placing the mind - we find our object and focus our mind on it. We have more distractions than concentration during our meditation session at this stage.
2) continual placement - we are able to hold our object of meditation single-pointedly for about five minutes. We still have many distractions, but less than on the first level. When we lose the object, we need to return to analytical meditation to find it again.
3) replacement - when we lose the object, we can immediately pick it back up again without returning to analytical meditation. Our mindfulness is much stronger and we can meditate for an hour without ever completely losing our object.
4) close placement - we do not forget our object of meditation at any time during the session.
5) controlling - there is no danger of mental excitement or gross mental sinking, but we develop subtle mental sinking when our mind becomes too inwardly gathered. We apply alertness to overcome the obstacle of subtle mental sinking.
6) pacifying - there is no danger of mental sinking or gross mental excitement, but we develop subtle mental excitement due to overapplication of the remedy to mental sinking on the level of controlling. We apply alertness to overcome the obstacle of subtle mental excitement.
7) completely pacifying - we have perfected the powers of mindfulness and alertness, and there is no great danger of subtle mental sinking or subtle mental excitement. If either obstacle arises it can immediately be eliminated through the power of effort.
8) single-pointedness - it is impossible for any mental sinking or mental excitement to develop during meditation. We can focus and remain single-pointedly on our object as long as we like, but we still need to exert effort to maintain concentration.
9) placement in equipoise - concentration is effortless to sustain and comes naturally and spontaneously. Only Buddhas have completed the perfection of effort and can accomplish all tasks effortlessly.